The use of androgenic-anabolic steroids is wide-spread among male athletes, and it is not uncommon among female athletes. While the immediate side effects of this practice are reasonably well documented, almost nothing is known about the long-term--i.e., lifetime--consequences of steroid abuse. This is a proposal to expose young adult male and female mice to androgenic-anabolic steroids and then survey the enduring consequences of this treatment in middle and old age. Specifically, starting at two months of age, CBF1 mice of both sexes will be given 6 months of cyclic exposure to either high or low doses of a "stacked" combination of four commonly-abused steroids. Some animals will be killed at 8, 12, or 24 months of age to look for effects on body composition, reproductive capability and the development of specific pathologies. Other mice will be tested at these same three ages to assess their spontaneous locomotor activity, strength and endurance, and sexual and aggressive behavior. These particular characteristics were chosen because they are all dependent to some degree on the organizing actions of androgen in normal males and the absence of these actions in normal females. Of particular importance in this set of experiments will be a careful documentation of any effect of steroid abuse on life span.